On tipping points and feedback loops

| September 8, 2010 | 3 Replies

Malcolm Gladwell popularized the concept of tipping points with his book The Tipping Point: How Little Things Can Make a Big Difference.  Although his book was mainly dealing with pop-psychology, the utility of the term has led to its spread throughout several disciplines.  But the arena where it has really come into its own is the environmental movement.

Scientists have struggled to find a way to explain complex environmental changes in ways that will make them comprehensible to the layperson.  The concept of tipping points is just such an explanation.  Wikipedia gives us an example of how tipping points can simplify the understanding of climate changes:

A climate tipping point is a point when global climate changes from one stable state to another stable state, in a similar manner to a wine glass tipping over. After the tipping point has been passed, a transition to a new state occurs. The tipping event may be irreversible, comparable to wine spilling from the glass—standing up the glass will not put the wine back.

In much the same way as you can gradually tip a wineglass to the side, climactic or ecological changes can accumulate slowly.  Once the tipping point is reached however, gravity or some analogous force takes control and the situation can change rapidly.

A related concept is that of “feedback loops“.  Changes in one area have consequences in other areas, and those consequences can amplify the effects of the changes in the first area.  The classic example of positive feedback in climate change is melting of the arctic permafrost caused by global warming.  The thawed permafrost releases methane gas (a potent greenhouse gas) which had been trapped in the frozen ground, which then increases global warming.

Another example– crops that are under stress from the effects of climate change also release methane at an accelerated rate.  A University of Calgary study found that  “when crops are exposed to environmental factors that are part of climate change — increased temperature, drought and ultraviolet-B radiation — some plants show enhanced methane emissions. Methane is a very potent greenhouse gas; 23 times more effective in trapping heat than carbon dioxide.”  So the released methane goes on to amplify the effects of global warming, continuing the feedback loop.

Understanding these two concepts (tipping points and feedback loops) are crucial to understanding climate and ecological science.  The problem is one of predicting where the tipping points are in advance.

To see how these factors work in a real-life situation, consider the phenomenon of “overfishing”.  There are two main ways that overfishing can seriously alter ecosystems.  First, fish of a certain species may be caught to the point where there are no longer sufficient adult fish to produce offspring, leading to a population crash.  The second way is through what’s known as “ecosystem overfishing”, where a certain species or type of species is fished until it changes the whole balance of an ecosystem.  For example, if large predatory fish are depleted, those changes can ripple through an ecosystem, perhaps leading to an abundance of smaller, foraging fish.

To see how rapidly these changes can take place, let’s look at the case of cod fishing off the coast of Canada.  This graph from Wikipedia shows the numbers of fish caught over the years.

The tipping point & collapse of cod. Image via Wikipedia

Cod had been caught in these waters for the past 500 years, but “sustainably”.  That is, the cod were caught at a low enough rate to allow for the fish stocks to replenish themselves.  Beginning in the 1950′s however, a number of factors converged which led to the eventual collapse of the cod populations.  Technology for fishermen was improving rapidly, and technologies like sonar imaging allowed fishermen to catch much greater numbers of fish than ever before.  Cod fishing was also important socially and economically to the area.  Many people took a part of their identity from being fishermen, and the economic impact of fishing is difficult to overstate.  However, our understanding of the ocean and its complex ecosystems had not kept pace with either the technology of fishing or the greed and myopia of the various stakeholders, and the cod population went into a steep decline.   Finally, in 1992, the Canadian government was forced to declare a moratorium on cod fishing after the biomass level had fallen to one percent of its former levels. The collapse of the fish stocks led to a similar collapse in the localities that depended upon the catch– Wikipedia notes that “in Newfoundland alone, over 35,000 fishers and plant workers from over 400 coastal communities became unemployed.”

Nor did very many people see the collapse coming.  The easy money from the catch and steadily-improving technological advances made it seem as if the area had won the jackpot.  The fish catch was improving yearly, and the warnings of scientist were ignored.  The BBC reports that we still have lessons to learn:

The alarming thing about the experience of Newfoundland is that despite 10 years of the moratorium, the cod still has not returned in significant numbers.

What no one knows is when or whether the old way of things will return.

So what are the lessons for the North Sea?

Marine scientist George Rose is concerned to hear European fishermen challenging the warnings of scientists because they can still find plenty of cod. This echoes the claims of trawlermen on the Grand Banks in the late 1980s, but it turned out that they were observing a phenomenon he calls “hyper-aggregation”, in which fish cluster in ever-greater densities when their environment is under pressure.

“If you look at the data on the catches-per-unit of the trawler fleet, the highest ever recorded in this fishery were in 1992, when the stocks were on the verge of collapse,” said Professor Rose.

“So if fishermen are still saying they can find concentrations, that’s good news for now, but it should give no reassurance that you couldn’t take those last bits of fish down and push the whole thing right over the edge.”

Nor are cod the only species where this type of collapse has happened.  The Atlantic salmon catch went from 4 million in 1979 to a mere 700,000 in 1990.  Today, if you buy a fish labeled “Atlantic salmon”, it’s likely to be a farmed fish, not a wild one.  But farmed salmon come with their own problems, leading to proposed solutions like the genetically modified salmon.  A recent article in Time magazine touting the franken-fish as a necessary evil points out just how precarious our situation is:

Fish species are the foundation for all ocean life, and no one can say what will happen to the world food chain if 90% of ocean life forms collapse, which is likely to happen by 2048, according to a study in the immensely prestigious journal Science. The main reason the study gave wasn’t global warming, or the great Pacific garbage patch or toxic runoff from industrial production. The reason was overfishing.

The collapse of 90% of ocean life forms is considered “likely”!?  Given the difficulties in predicting the tipping point in the collapse of fish stocks, it’s imperative that we do everything possible to avert this collapse.  But why is it that creating a new fish by inserting genes from other organisms is considered prudent, even necessary, while stopping the damage to the fisheries is not even on the table? After all, if we stopped the damage to the natural ecosystems, we could allow them time to replenish themselves, meaning the need for genetically-modified fish would disappear.

It’s not just ocean life that’s at risk– a recent survey of freshwater fish in Africa found that between one-fifth and one-half of freshwater species are at risk of extinction.

About 7.5 million people in sub-Saharan Africa are thought to depend on fisheries.

“If we don’t stem the loss of these species, not only will the richness of Africa’s biodiversity be reduced forever, but millions of people will lose a key source of income, food and materials,” warned William Darwall, manager of the IUCN’s freshwater biodiversity unit.

Fisheries around the world are at risk– it’s truly a global problem.  Even before the Deepwater Horizon disaster, the Gulf of Mexico was in big trouble.  This trouble stems from a dead zone which is threatening the collapse of the Gulf ecosystem.  Fertilizer runoff that is brought to the Gulf from the Mississippi river creates algae blooms which pull oxygen from the water.  Fish cannot survive in this type of environment, so they either die or move elsewhere. A recent story on CNN explains the phenomenon and its impacts:

As summer approaches and the Louisiana air gets hot and wet, Dean Blanchard says, he can tell that the dead zone is forming because shrimp leap onto the beach.

“They pretty much commit suicide,” he says.

Blanchard, who owns a large-scale seafood wholesaling business in Grand Isle, Louisiana, says he never saw that phenomenon until six or seven years ago.

Scientists first recorded an oxygen-dead zone in the Gulf in 1972. Since then, the size of this underwater coffin has fluctuated, but it is growing. In 2009, the dead zone smothered an area of about 3,000 square miles. This year, it is more than twice as big — and is the fifth largest on record, according to the National Oceanic and Atmospheric Administration, which monitors the area.

The longer the phenomenon persists, the weaker the Gulf ecosystem becomes, said Rob Magnien, director of the Center for Sponsored Coastal Ocean Research at NOAA.

“If the area grows large enough, the consequence is, at some point, we’ll reach a tipping point where some of our major commercial and recreational species [of fish, shrimp and oysters] would be severely affected,” he said.

No one knows for sure when the Gulf will cross that threshold, but the wait may not be long, Magnien said. Early testing indicates that the ocean ecosystem is already under intense stress: It takes less fertilizer pollution today, for example, to produce a large dead zone in the Gulf than it did several years ago.

That’s a sign that the dead zone will continue to grow unless fertilizer levels are cut drastically.

In the meantime, people in the Gulf seafood industry, like Blanchard, say they have to work around the dead zone each summer. Blanchard says he loses up to $250,000 of his $35 million total revenue per year because of the phenomenon.

And shrimpers may not be able to avoid the zone forever.

“They avoid the dead zone areas and are able to catch shrimp in other areas, but at some point, the zone is going to grow to a size where they can’t reach the shrimp anymore or they simply have insufficient habitat to maintain a robust population,” Magnien said.

The one hopeful thing about our situation is that feedback loops and tipping points work both ways.  Feedback loops can start to work in our favor, rather than against us, if we only give them a chance.  A 2006 article explaining how feedback loops are likely to mean higher temperatures than most models are accounting for explains how this could work:

The feedback loop from greenhouse gas concentrations also has a reverse effect, the authors state, in that reduced atmospheric levels can enhance the cooling of global temperatures. This presents at least the possibility of extra rewards if greenhouse gas levels in the atmosphere could be rolled back, but the challenge is great as Harte explained.

“If we reduce emissions so much that the atmospheric concentration of carbon dioxide actually starts to come down and the global temperature also starts to decrease, then the feedback would work for us and speed the recovery,” Harte said. “However, if we reduce emissions by an amount that greatly reduces the rate at which the carbon dioxide level in the atmosphere increases, but don’t cut emissions back to the point where the carbon dioxide level actually decreases, then the positive feedback still works against us.”

Whatever the case, we must take action soon to prevent a series of crucial tipping points from being breached.  Once we cross that threshold, the ramifications are difficult or unpleasant to predict.


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Category: Environment, Risks and Dangers, Sustainable Living

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is a full-time wage slave and part-time philosopher, writing and living just outside Omaha with his lovely wife and two feline roommates.

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  1. Great Garbage Patch of the Atlantic | January 8, 2011
  1. Erich Vieth says:

    One way to slow the devastation is to realize the extent to which we are a throw away culture. http://www.recycle.co.uk/throw-away.html

    We haven't yet begun to fight the devastation, though. Not really. The question is whether we ever will or whether we have become quietly resigned. I suspect that we won't turn this mess around, because there is too much evidence that we are living as though there is no tomorrow. I hope I'm wrong.

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